I. Field of the Invention
The present invention relates to dynamic configuration of local area networks (LANs) and, more particularly, to a method of LAN configuration to enable full-bandwidth communications among selected computing equipment. In addition, the invention concerns an apparatus and method for allocating private connections via a LAN switching mechanism.
II. Background of the Invention
In today's complex computing and data communications environments, there is an ever-growing need for high-speed data transfer. For example, image (video) transmission requires a vast amount of data to be transmitted across a network and drives the need for high-speed data transfer. Image transmission is required in tools such as computer-aided engineering software, for such applications as solid modeling, computer-aided electronic design, and visualization. Even greater network performance is necessary where video and audio information are transmitted across networks in applications such as teleconferencing, education, marketing, news, and entertainment.
Of particular interest are those network applications which are primarily client/server sessions (such as in a local area network (LAN)), with audio and image streams being continuously transmitted from the server to the client. In most of today's network systems, the video and audio data transfer requires a large amount of the available network transmission bandwidth, leaving little bandwidth for other sessions.
Data compression is one method of freeing up some of the bandwidth absorbed by the video/audio data transfer (real-time compression is available today at 160:1) but inherently results in a loss of at least some data. In many applications, lossy compression is tolerable. Other applications can tolerate only lossless compression, thereby requiring exclusive use of a substantial portion of the available transmission bandwidth.
For example, although both Ethernet (10 Mbps) and Token Ring (4/16 Mbps) LANs can transmit compressed image, neither network can sustain more than a handful of live-running video sessions. Indeed, some applications that require high-quality image may necessitate the dedication of the complete LAN bandwidth to a single user. Thus, given current LAN topologies, those with multiple units attached on a bus or a ring, it is conceivable that several multimedia users could consume the entire bandwidth, thereby creating performance problems with other traffic on the network.
Another method of providing the necessary bandwidth is to utilize higher-speed technology. For instance, the Fiber Distributed Data Interface (FDDI) increases the LAN transmission capability from 16 Mbps to 100 Mbps (raw capacity). Further, FDDI-2 offers time multiplexing to reduce the protocol overhead. FDDI and FDDI-2 are, however, expensive to install, especially where the network components are already established.
Another method of guaranteeing bandwidth is limiting the amount of video data transmitted by reducing the image size or the number of frames per second being transmitted. This solution is acceptable for only niche applications. The primary problem with reducing size is that of comprehending the image. Historically, frame speeds below cinematographic or NTSC standards have been shown to be ineffective and unusable.
Another approach to guaranteeing full bandwidth to end users is the use of what is called an "intelligent hub". This network device connects each user with a dedicated LAN interface, for example, an Ethernet bus, which results in each user being assured free use of the available LAN bandwidth, 10 Mbps in this example. Data is transferred from one user to another via bridging. The bridging process, however, introduces delays (latency) that are detrimental to some multimedia applications. In addition, although an intelligent hub may be somewhat effective in that existing cable media and terminal communications adapters can be used, the cost for these devices can be prohibitive.
Reconfiguration of a network, which can be accomplished by rearranging the interconnections on a LAN, for example, is a method of providing necessary LAN bandwidth for its corresponding LAN stations. For example, if performance is poor, the network may be divided into two or more "subLANs" and then interconnected with a bridge. In this way, each subLAN has the maximum LAN bandwidth and, therefore, each station has less competition for the available bandwidth.
In a Token Ring network, this reconfiguration is accomplished by rearranging the connections at the multistation access units (MAUs) which are utilized to provide the appropriate connectivity. Presently, however, this process must be done manually and is, by no means, dynamic.
The challenge is to develop a method to manage the bandwidth of a low-cost network that will permit multimedia (audio/video) communications along with other, less demanding traffic.